In order to protect substances such as food and beverages from contamination, a coating is typically applied to the inside surfaces of containers in which such substances are stored. This coating prevents the contents of the container from coming into direct contact with the bare metal or plastic interior surfaces of the container. With standard cylindrical containers or cans, this coating is generally applied to the interior of the container before the top is affixed through the use of a spray nozzle which is arranged to discharge through the open end of the container. As the coating is being discharged from the nozzle, the container is rotated about its longitudinal axis so as to ensure that all of the interior surfaces are coated.
The coating material used on the inside surfaces of the containers represents one of the most significant costs associated with a container manufacturing operation. To help achieve an even coating, the coating material is generally applied using spray nozzles that are configured to produce an asymmetrical distribution of the fluid discharge. In particular, the nozzles generally produce a fan-shaped discharge pattern with a maximum amount of fluid being discharged at a point offset from the center of the spray pattern and with the level or amount of discharge tapering from the location of maximum discharge to either end of the spray pattern. These nozzles are arranged at an angle relative to the longitudinal axis of the container so that the heaviest portion of the discharge is directed towards the far, closed end of the container. Thus, the asymmetrical distribution helps compensate for the greater distance the coating material must travel to reach the closed end of the container and, in turn, the greater surface area of the interior of the container that this portion of the discharge pattern must cover.
Because of the asymmetrical distribution of the fluid discharge, the spray nozzles must be arranged in a specific orientation relative to the containers to achieve the desired even coating of the interior of the containers. If the orientation of the spray nozzles is incorrect, the containers will not be properly coated. A container coating operation typically is highly automated. Thus, when one or more of the spray nozzles applying the coating is installed incorrectly, a significant amount of time may elapse before the problem is discovered. Because a container coating operation also runs at a very high speed, thousands of containers may be coated improperly during this time. Once the alignment problem with the spray nozzles is corrected, the defective containers then have to be collected and recoated. Obviously, this is an expensive and time consuming process.
Currently, the standard practice for indicating the proper alignment of the spray nozzle is to place an arrow on the body of the nozzle. However, in a container coating operation, a build-up of the container coating material can quickly form on the spray nozzles. This build-up can obscure the arrow on the nozzle body making it difficult to determine if the nozzle is installed properly.